Force 7 Ocean Wave

III) Aero-Hydro Trim Froude 0.50 and Froude 0.60 Model

Ludwig Prandtl, Savitsky, Keuning and i

IV) the firm conviction that a yacht's fundamental centers must be reconciled:

Center of Flotation, Center of Buoyancy, Center of Gravity and hydroDynamic Center of the Keel

We orthodox ... have been waiting for 55 years for the extravagant troglodytes (1970-) to explain why they think it's reasonable to sail with the Keel's hydroDynamic Center at around 40%, the Yacht Center of Gravity at around 50% and the Center of Flotation at around 60%

V) Put a comfortable seat on a Mini-Transat, a staysail with boom, and a bowsprit that pivots aft.

Of course, the sailor has to lift his or her butt off the comfortable seat. Cruelty on the part of the designer.

 

1976

"One Ton Cup"

The explanation is very simple: the races that set the trend were in the summer and were won upwind.

The entire design was optimized or sacrificed to 10-16 knots upwind.

This created a paradigm that became the standard, and it seems difficult to escape from it.

 

The Mini Transat freed us

But many slower 10-square-meter-per-ton yachts have only learned to have a very wide stern to create more cabin space.

 

In a small, light boat with a bowsprit we can comfortably hoist a soft nylon 'scarf' of 9 square meters and we have 30 square meters per ton (!)

When I went bankrupt, I stopped sailing yachts and bought an old mini transat.

And I don't want anything else.

If I were a millionaire again, I wouldn't go back to yachting.

But I don't see myself at 70 years old on the deck of a small, light boat.

A mini transat with the mast close to the cockpit, a staysail with a boom, a bowsprit that turns aft, retractable appendages for approaching shallow waters, and comfortable seats seems like a great idea for an old sailor.

 

So the "in-out" sections on this are reasonably "balanced"?
I almost drove my self bat-shyte crazy counting squares on graph paper doing heeled analysis, which at the time seemed preferable to learning a new software programme.
Your interior layout makes sense.

 

Note how the bow has evolved in S1 since the first version to obtain more hydrodynamic lift

... and better "in-out"

 

The combination of

+ a low chine at the bow and a high chine at the stern ...
+ a wide bow... and
+ the Longitudinal position of the Centers

L_CF: 58% LWL
L_CB: 60%
L_CG: 62%

The boat is almost almost ... a British Classic, haha

Denys Rayner

Denys Rayner - Wikipedia https://en.wikipedia.org/wiki/Denys_Rayner

Thomas Harrison Butler

Thomas Harrison Butler - Wikipedia https://en.wikipedia.org/wiki/Thomas_Harrison_Butler

 

Well

1) It's almost almost almost a British classic, meaning the boat is well-founded in a very very Solid Tradition.

2) It also has a longitudinal metacentric height of astronomical size: more than 18 meters, 3 (!) x LWL: This means that if the bow dips 1 degree, the Center of Buoyancy moves 30 cm (5% LWL) and

3) the bow produces a lot of hydrodynamic Lift when accelerating (Fn > 0.50)

Even if the dynamic estimates aren't very precise, the design is so carefully considered that it borders on exaggerated exaggeration (?) from the point of view of Prudence and Respect for ocean waves

 

Mr. Max Michael Munk

Max Munk - Wikipedia https://en.wikipedia.org/wiki/Max_Munk

Munk Moment

Munk Moment as a Vector at Stem

 

Four-way cloud estimates (arithmetic mean) assuming a 6-degree Yaw/Leeway and various speeds:

1) Prof. Kensaku Nomoto (Osaka University) + Prof. Keuning (Delft) [my simplification]

2) Prof. Alexander H Day (University of Strachclyde) I'm not including it because it's too long and could be confusing.

3) My simplification from JW Slooff

4) A simple reasoning based on Hörner (Fluid Dynamic Lift; Fluid Dynamic Drag): Linear Lift of a "slender body or very low aspect ratio wing" + "non-linear component" (x 1.4)

q: dynamic pressure
h: hull depth

 

Speed: 4 m/s
Leeway/Yaw: 6°
h: 0.21 m

H =

1) 308 Newtons
2) 300 Newtons
3) 328 Newtons
4) 278 Newtons



In the end, the main issue is to Neutralize the keel, that is: the hydrodynamic center of the keel must be below the center of gravity of the yacht.

 

When accelerating (Fn 0.50 - Fn 0.60) the bow emerges from the water and rides on top of the bow-wave.

The stern is enormously wide to support the sails and allow the water to exit straight without creating Lateral low pressure.

Frank Bethwaite, High Performance Sailing:

"The first change was the elimination of the small stern (...) the inward curves lead to uncontrolable 'dutch rolling' at speed"

When the hull is trimmed stern down, the water exit is completely straight when viewed from above.

The Munk Moment then tends to zero, and the Keel is Neutralized.

The boat can be steered by a child or a brain-dead autopilot, and in any case, it's a delight that gives peace of mind when you feel its good behavior, not the horrors we cruisers have endured.

 

"the horrors we cruisers have endured"

The Dinosaur

To begin with, it's slow relative to its length/LWL; it has a difficult start to overcome the bow-wave.

Its Munk Moment is very large.

Heel sinks the bow, and the Ocean wave sinks the bow.

When you add Pitch, the Munk Moment is multiplied by Two.

Furthermore, the hydrodynamic center of the keel has a huge lever arm relative to the yacht's center of gravity.

And to top it all off, a solitary rudder blade swallows the down/sidewash and the vortex of the keel.

Downwash - Wikipedia https://en.wikipedia.org/wiki/Downwash

 

To Canary islands
Force 7

Brand new 45 ft Dinosaur
1 naval architect + 1 seasick wife + seasick friends = 1
2 very expensive autopilots

Result:
1 naval architect 16 hours chained to the wheel

Old 19.19 ft boat
1 sailor

Result:
peak Surf: 20 knots




The project was to cross the Atlantic and make a documentary, a film.

But although the project wasn't completed, it exceeded all expectations in the technical hydrodynamics on the Atlantic Wave Tank, confirming what Andy Claughton had already told us in 1984* during his research in the Southampton Wave Tank.

---

*: I mean, the investigation took place around that time. I found out about 10 years ago.

 

Until very recently, Mini Transat Hulls were horribly unbalanced.

But it wasn't noticeable because they hoist 30-60 square meters per ton downwind, so the speed and hydrodynamic lift hide the hydrostatic imbalance.

The problem arises when a slow, 10-square-meter-per-ton Dinosaur imitates a Mini Transat and, to top it all off, leaves the Keel as if it were going to the 1975 One Ton Cup.